Determining wire sizes

[prattz99]

Hi i'm studding the code trying to make a possible carrier out of the trade and I don't understand how to determine wire size for long runs. I know you need to factor in length of the run and the current used but I just don't get it, is there a table you use or a formula voltage drop? I'm just at a lose with it all any help would be of great use. Thanks

 

[augie47]

Welcome to the Forum:
If you go to Mike Holt's home page and look (in the free stuff, as I recall) you will find a formula for voltage drop.
Once you have calculated your load, you can plug in the numbers and it will give you the wire size for a given % of drop.
Keep in mind the NEC has suggestions on voltage drop, but there is no NEC requirement to keep it at any particular %. (see NEC 210.19)

 

[jumper]

Welcome, I will let the more experienced members answer your question, but you might find these formulas useful in your studies:
http://www.mikeholt.com/documents/freestuff/ElectricalFormulas.pdf

 

[dmagyar]

Voltage drop is dependant on several variables

Voltage drop is dependant on several variables

One reason that there isn't a convenient table is that length, wire cross section or size and amperage or load all contribute to the calculations for voltage drop.

 

[cadpoint]

Here is a 2003 explanation by the host of this forum Here

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